异苯并二氢吡喃衍生物新合成方法的研究

用新方法合成了一系列异苯并二氢吡喃衍生物。其特点是产率高, 反应时间短, 成本低, 污染小。所合成的异色满麝香均经元素分析, 红外光谱和核磁共振谱予以证实。     

On the method of reflection and short in dielectric time domain spectroscopy

The method of reflection against a sample and short in dielectric time domain spectroscopy (TDS) is discussed. It is shown how, by a proper choice of sample lengths, the method can be used to reach even the high-frequency end of the spectrum accessible by TDS. Results for test measurements on benzyl alcohol and chlorobenzene are given.     

Stochastic surrogate Hamiltonian

The surrogate Hamiltonian is a general scheme to simulate the many body quantum dynamics composed of a primary system coupled to a bath. The method has been based on a representative bath Hamiltonian composed of two-level systems that is able to mimic the true system-bath dynamics up to a prespecified time. The original surrogate Hamiltonian method is limited to short time dynamics since the size of the Hilbert space required to obtain convergence grows exponentially with time. By randomly swapping bath modes with a secondary thermal reservoir, the method can simulate quantum dynamics of the primary system from short times to thermal equilibrium. By averaging a small number of realizations converged values of the system observables are obtained avoiding the exponential increase in resources. The method is demonstrated for the equilibration of a molecular oscillator with a thermal bath.     

Semiclassical tunneling splittings from short time dynamics: Herman-Kluk-propagation and harmonic inversion

We investigate a recently proposed method [J. Chem. Phys. 108, 9206 (1998)] to obtain tunneling splittings from short time cross-correlation matrices that were propagated according to the semiclassical propagator of Herman and Kluk. The energy levels were extracted by harmonic inversion of the cross-correlation matrix using the filter diagonalization technique. The aim of this study is twofold: First, the short time behavior of the Herman-Kluk-propagator and the meaning of using cross-correlation matrices rather than autocorrelation functions is addressed. Numerical examples are given for one- and two-dimensional model potentials. Second, the performance of the method is investigated for a system with considerable anharmonicity and coupling. Here the proton transfer in 3,7-dichlorotropolone is considered using an ab initio reaction surface Hamiltonian approach. For this example also the extension to more dimensions is critically discussed.     

Long-Lived Coherence Originating from Electronic-Vibrational Couplings in Light-Harvesting Complexes

We theoretically investigate the evolutions of two-dimensional, third-order, nonlinear pho-ton echo rephasing spectra with population time by using an exact numerical path integral method. It is shown that for the same system, the coherence time and relaxation time of excitonic states are short, however, if the couplings of electronic and intra-pigment vibra-tional modes are considered, the coherence time and relaxation time of this vibronic states are greatly extended. It means that the couplings between electronic and vibrational modes play important roles in keeping long-lived coherence in light-harvesting complexes. Particularly, by using the method we can fix the transition path of the energy transfer in bio-molecular systems.     

A Convenient Method for Dehydrogenation of Symmetric Hydrazo Compounds

A convenient method using FeCl₃ as oxidant to dehydrogenate symmetric hydrazo compounds is reported for the first time. The method is superior to other known methods for dehydrogenating ArNHNHAr. It needs only cheap and less toxic reagents, mild conditions and short reaction time. Eight symmetric azo compounds are prepared in good yields.     

Computer-assisted reactor NAA of geological and other reference materials,using the k0-standardization method: Evaluation of the accuracy

A scheme for instrumental neutron activation analysis of ancient and medieval glasses is proposed. The combination of three irradiations (short time, pile and epithermal) enables the determination of 34 elements. The accuracy of the method is evaluated by analyzing two glass standard reference materials. Results from the analysis of three glasses from different times are presented.     

Influence of hydrodynamic coupling on the density dependence of quasi-one-dimensional diffusion

The effect on the short time one particle diffusion coefficient of hydrodynamic interaction between pairs of colloid particles, and between colloid particles and the walls of a quasi-one-dimensional cylindrical channel, are calculated using the method of reflections. The nonzero size of the colloid particle is accounted for in the analysis, and the theoretical predictions are compared with the experimental data of Lin, Cui, Lee, and Yu for the short time one particle diffusion coefficient of colloids in a square open channel [Europhys. Lett. 57, 724 (2002)].     

One‐pot Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones Catalysed by Cupric Acetate under Solvent‐free Conditions

A solvent‐free synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones from aromatic aldehydes, β‐keto ester/acetyl acetone and urea catalysed by cupric acetate under thermal condition is reported as a simple and an efficient protocol. Compared with classical Biginelli reaction reported in 1893, this new method provides much improved modification in terms of yield and reaction time. The usage of milder catalyst, environmental friendly procedures and excellent yields within a very short time (5–15 min) are the advantages of the method in which the involvement of solvent‐free condition adds an edge to the method. Thus, the efficiency of the protocol enabled the rapid synthesis of 3,4‐dihydropyrimidin‐2(1H)‐one derivatives in a short duration.     

A fast fourier transform method for calculating the equilibrium density matrix

We calculate the low-temperature quantum density matrix by integrating numerically the Bloch equation. The initial condition is the classical high-temperature value of the density matrix. The integration method uses short “time” propagators computed by a fast Fourier transform method.     

水溶液中微波辅助下5-碘嘧啶类化合物的合成

5-碘嘧啶类衍生物具有显著的化学治疗活性和有机合成用途。碘苷(又名疱疹净)于1962年被美国FDA批准用于治疗疱疹病毒角膜炎,这是第一个抗单纯疱疹病毒药物[1]。以碘苷为中间体可以合成其它高效低毒的抗病毒药物[2]。另外,通过Suzuki、Sonogashira等金属催化偶联反应可以在5位引     

Shear free and blotless cryo-TEM imaging: a new method for probing early evolution of nanostructures

Cryogenic transmission electron microscopy (cryo-TEM) is a powerful method to image native state morphologies of nanoscale soft and hard objects suspended in solvents. Sample preparation is a critical step toward producing images at length and time scales of interest. We demonstrate a nearly shear-free sample thinning method which simultaneously allows imaging of evolving nanostructures at subsecond time scales. This device breaks the trade-off between high shear and short time scales typical in current cryo-TEM sample preparation methods. We demonstrate the low-shear feature of the new method by imaging wormlike micelles, showing an interconnected network, in contrast to the traditional sample preparation method which shows aligned micelles at similar time points. The time resolution of this method is demonstrated by imaging morphologies of calcium carbonate (formed through the reaction of calcium chloride with sodium carbonate) at subsecond time scales, capturing its evolution from an amorphous to a crystalline state. The impact of hyperbranched polyglycerol additives on the amorphous to crystalline transition in calcium carbonate at short times is examined. Early images at low shear provide unique fundamental insights into mechanisms of nanostructure evolution, thus offering a new paradigm for research in materials sciences, soft matter, and biological sciences.     

Rapid radiochemical sample preparation for alpha spectrometry using polymer ligand films

Rapid radioanalytical methods are adversely affected by many different sample-matrix interferences, which make analyzing samples a difficult and time consuming process. A new method for preparing radioactive samples for analysis by alpha spectrometry has been demonstrated. In this technique, a selective extractive ligand is immobilized in a polymer film coated on a metal surface. This polymer ligand film is then used to extract plutonium and other radioactive analytes from solution over a short period of time. The prepared substrate is then counted directly by alpha spectroscopy in a small single detector alpha spectrometer. The method has been demonstrated for the analysis of americium and plutonium in liquid samples such as water and urine.     

Electrochemical microstructuring with short voltage pulses.

The application of short (nanosecond) voltage pulses between a tool electrode and a work piece immersed in an electrolyte solution allows the three-dimensional machining of electrochemically active materials with submicrometer resolution. The method is based on the finite charging time constant of the double-layer capacitance, which varies approximately linearly with the local separation between the electrode surfaces. Hence, the polarization of the electrodes during short pulses and subsequent electrochemical reactions are confined to regions where the electrodes are in sufficiently close proximity. This Minireview describes the principles behind electrochemical micro-structuring with short voltage pulses, and its current achievements and limitations.     

Magnetic rotational spectroscopy with nanorods to probe time-dependent rheology of microdroplets

In situ characterization of minute amounts of fluids that rapidly change their rheological properties is a challenge. In this paper, the rheological properties of fluids were evaluated by examining the behavior of magnetic nanorods in a rotating magnetic field. We proposed a theory describing the rotation of a magnetic nanorod in a fluid when its viscosity increases with time exponentially fast. To confirm the theory, we studied the time-dependent rheology of microdroplets of 2-hydroxyethyl-methacrylate (HEMA)/diethylene glycol dimethacylate (DEGDMA)-based hydrogel during photopolymerization synthesis. We demonstrated that magnetic rotational spectroscopy provides rich physicochemical information about the gelation process. The method allows one to completely specify the time-dependent viscosity by directly measuring characteristic viscosity and characteristic time. Remarkably, one can analyze not only the polymer solution, but also the suspension enriched with the gel domains being formed. Since the probing nanorods are measured in nanometers, this method can be used for the in vivo mapping of the rheological properties of biofluids and polymers on a microscopic level at short time intervals when other methods fall short.     

One‐pot Four‐component Synthesis of Highly Functionalized Pyridines Using Nitroketene Dithioacetal as a Source of Methyl Thiolate Under Solvent‐free Condition

A simple method for the synthesis of highly functionalized 2‐amino‐6‐(methylthio)pyridine‐3,5‐dicarbonitriles is presented. In this method, pyridine derivatives are synthesized from the reaction of malononitrile, aromatic aldehydes, nitroketene dithioacetal in the presence of ethylene diamine. The notable features of this method are the simple Experimental procedure, short reaction time, and good yields.     

A new method for measuring the diffusion coefficient in a gas phase

A new and fast method for measuring the diffusion coefficients of binary gas mixtures using ion mobility spectrometry (IMS) has been developed. In this method, the sample is injected as a short pulse into the flowing drift gas, forming a Gaussian concentration profile inside the drift region. This Gaussian cloud is irradiated with a fast moving swarm of electrons to create negative ions. The flash of electrons is so short that the negative ions do not move much during the exposure time. The ions then drift toward the detector, where they are collected. The collected ion signal pattern reflects the spatial distribution of the sample inside the cloud at the time of exposure. This is repeated in intervals of 300-400 ms to monitor the spatial spreading of the molecules in the drift region. Consecutive IMS spectra show the evolution of the cloud over time. The collected spectra are fit to Gaussian functions to extract diffusion coefficients. Using this method, the diffusion coefficient of O(2), CHCl(3), and C(2)H(2)Cl(2) were measured, and the results are in good agreement with the previously reported experimental data.     

Extension of The Applicability of Jäntti's Method For Fast Calculation of Adsorption Data

The time for adsorption measurements can be substantially reduced by measuring several values at short time intervals at the beginning of the kinetic curve and extrapolation of the equilibrium value. The method used by Jäntti for simple adsorption processes has been extended for complicated processes using a second order differential equation. A simulated example is calculated.     

Colloidal dynamics near a wall studied by evanescent wave light scattering: experimental and theoretical improvements and methodological limitations

The dynamics of colloidal spheres near to a wall is studied with an evanescent wave scattering setup that allows for an independent variation of the components of the scattering wave vector normal and parallel to the wall. The correlation functions obtained with this novel instrumentation are interpreted on the basis of an expression for their short time behavior that includes hydrodynamic interactions between the colloidal spheres and the wall. The combination of the evanescent wave scattering setup and the exact expression for the short time behavior of correlation functions allows for an unambiguous measurement of the particle mobility parallel and normal to the wall by means of light scattering. It is possible to measure the viscous wall drag effect on the dynamics of particles with radii as small as 27 nm, where, however, the method reaches its limits due to the low scattering intensities of such small particles.